Dualism and monism are the two major schools of thought that attempt to resolve the mind-body problem. Dualism is the position that mind and body are in some categorical way separate from each other. It can be traced back to Plato,[2]Aristotle[3][4][5] and the Sankhya and Yoga schools of Hindu philosophy,[6] but it was most precisely formulated by René Descartes in the 17th century.[7]Substance dualists argue that the mind is an independently existing substance, whereas Property dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.[8]

Monism is the position that mind and body are not ontologically distinct kinds of entities. This view was first advocated in Western Philosophy by Parmenides in the 5th century BC and was later espoused by the 17th century rationalistBaruch Spinoza.[9]Physicalists argue that only the entities postulated by physical theory exist, and that the mind will eventually be explained in terms of these entities as physical theory continues to evolve. Idealists maintain that the mind is all that exists and that the external world is either mental itself, or an illusion created by the mind. Neutral monists adhere to the position that there is some other, neutral substance, and that both matter and mind are properties of this unknown substance. The most common monisms in the 20th and 21st centuries have all been variations of physicalism; these positions include behaviorism, the type identity theory, anomalous monism and functionalism.[10]

Many modern philosophers of mind adopt either a reductive or non-reductive physicalist position, maintaining in their different ways that the mind is not something separate from the body.[10] These approaches have been particularly influential in the sciences, especially in the fields of sociobiology, computer science, evolutionary psychology and the various neurosciences.[11][12][13][14] Other philosophers, however, adopt a non-physicalist position which challenges the notion that the mind is a purely physical construct. Reductive physicalists assert that all mental states and properties will eventually be explained by scientific accounts of physiological processes and states.[15][16][17]Non-reductive physicalists argue that although the brain is all there is to the mind, the predicates and vocabulary used in mental descriptions and explanations are indispensable, and cannot be reduced to the language and lower-level explanations of physical science.[18][19] Continued neuroscientific progress has helped to clarify some of these issues. However, they are far from having been resolved, and modern philosophers of mind continue to ask how the subjective qualities and the intentionality (aboutness) of mental states and properties can be explained in naturalistic terms.[20][21]

The mind-body problem

The mind-body problem concerns the explanation of the relationship that exists between minds, or mental processes, and bodily states or processes.[1] One of the aims of philosophers who work in this area is to explain how a supposedly non-material mind can influence a material body and vice-versa.

Our perceptual experiences depend on stimuli which arrive at our various sensory organs from the external world and these stimuli cause changes in our mental states; ultimately causing us to feel a sensation, which may be pleasant or unpleasant. Someone's desire for a slice of pizza, for example, will tend to cause that person to move their body in a specific manner and in a specific direction to obtain what they want. The question, then, is how it can be possible for conscious experiences to arise out of a lump of gray matter endowed with nothing but electrochemical properties.[10] A related problem is to explain how someone's propositional attitudes (e.g. beliefs and desires) can cause that individual's neurons to fire and his muscles to contract in exactly the correct manner. These comprise some of the puzzles that have confronted epistemologists and philosophers of mind from at least the time of René Descartes.[7]

Dualist solutions to the mind-body problem

Dualism is a set of views about the relationship between mind and matter. It begins with the claim that mental phenomena are, in some respects, non-physical.[8] One of the earliest known formulations of mind-body dualism was expressed in the eastern Sankhya and Yoga schools of Hindu philosophy (c. 650 BCE), which divided the world into purusha (mind/spirit) and prakrti (material substance).[6] Specifically, the Yoga Sutra of Patanjali presents an analytical approach to the nature of the mind.

In Western Philosophy, the earliest discussions of dualist ideas are in the writings of Plato and Aristotle. Each of these maintained, but for different reasons, that man's "intelligence" (a faculty of the mind or soul) could not be identified with, or explained in terms of, his physical body.[2][3] However, the best-known version of dualism is due to René Descartes (1641), and holds that the mind is a non-extended, non-physical substance.[7] Descartes was the first to clearly identify the mind with consciousness and self-awareness, and to distinguish this from the brain, which was the seat of intelligence. He was therefore the first to formulate the mind-body problem in the form in which it still exists today.[7]

Arguments for dualism

The main argument in favor of dualism is that it seems to appeal to the common-sense intuition of the vast majority of non-philosophically-trained people. If asked what the mind is, the average person will usually respond by identifying it with their self, their personality, their soul, or some other such entity. They will almost certainly deny that the mind simply is the brain, or vice-versa, finding the idea that there is just one ontological entity at play to be too mechanistic, or simply unintelligible.[8] The majority of modern philosophers of mind think that these intuitions, like many others, are probably misleading and that we should use our critical faculties, along with empirical evidence from the sciences, to examine these assumptions and determine if there is any real basis to them.[8]

Another important argument in favor of dualism is the idea that the mental and the physical seem to have quite different, and perhaps irreconcilable, properties.[22] Mental events have a certain subjective quality to them, whereas physical events do not. So, for example, one can reasonably ask what a burnt finger feels like, or what a blue sky looks like, or what nice music sounds like to a person. But it is meaningless, or at least odd, to ask what a surge in the uptake of glutamate in the dorsolateral portion of the hippocampus feels like.

Philosophers of mind call the subjective aspects of mental events qualia (or raw feels).[22] There is something that it is like to feel pain, to see a familiar shade of blue, and so on. There are qualia involved in these mental events that seem particularly difficult to reduce to anything physical.[23]

Interactionist dualism

Interactionist dualism, or simply interactionism, is the particular form of dualism first espoused by Descartes in the Meditations.[7] In the 20th century, its major defenders have been Karl Popper and John Carew Eccles.[24] It is the view that mental states, such as beliefs and desires, causally interact with physical states.[8]

Descartes' famous argument for this position can be summarized as follows: Seth has a clear and distinct idea of his mind as a thinking thing which has no spatial extension (i.e., it cannot be measured in terms of length, weight, height, and so on). He also has a clear and distinct idea of his body as something that is spatially extended, subject to quantification and not able to think. It follows that mind and body are not identical because they have radically different properties.[7]

At the same time, however, it is clear that Seth's mental states (desires, beliefs, etc.) have causal effects on his body and vice-versa: A child touches a hot stove (physical event) which causes pain (mental event) and makes him yell (physical event), this in turn provokes a sense of fear and protectiveness in the mother (mental event), and so on.

Descartes' argument crucially depends on the premise that what Seth believes to be "clear and distinct" ideas in his mind are necessarily true. Many contemporary philosophers doubt this.[25][26][27] For example, Joseph Agassi believes that several scientific discoveries made since the early 20th century have undermined the idea of privileged access to one's own ideas. Freud has shown that a psychologically-trained observer can understand a person's unconscious motivations better than she does. Duhem has shown that a philosopher of science can know a person's methods of discovery better than he does, while Malinowski has shown that an anthropologist can know a person's customs and habits better than he does. He also asserts that modern psychological experiments that cause people to see things that are not there provide grounds for rejecting Descartes' argument, because scientists can describe a person's perceptions better than he can.[28]

Other forms of dualism

Three varieties of dualism. The arrows indicate the direction of the causal interactions. Property dualism is not shown.

1) Psychophysical parallelism, or simply parallelism, is the view that mind and body, while having distinct ontological statuses, do not causally influence one another. Instead, they run along parallel paths (mind events causally interact with mind events and brain events causally interact with brain events) and only seem to influence each other.[29] This view was most prominently defended by Gottfried Leibniz. Although Leibniz was an ontological monist who believed that only one type of substance, the monad, exists in the universe, and that everything is reducible to it, he nonetheless maintained that there was an important distinction between "the mental" and "the physical" in terms of causation. He held that God had arranged things in advance so that minds and bodies would be in harmony with each other. This is known as the doctrine of pre-established harmony.[30]

2) Occasionalism is the view espoused by Nicholas Malebranche which asserts that all supposedly causal relations between physical events, or between physical and mental events, are not really causal at all. While body and mind are different substances, causes (whether mental or physical) are related to their effects by an act of God's intervention on each specific occasion.[31]

3) Epiphenomenalism is a doctrine first formulated by Thomas Henry Huxley.[32] It consists in the view that mental phenomena are causally ineffectual. Physical events can cause other physical events and physical events can cause mental events, but mental events cannot cause anything, since they are just causally inert by-products (i.e. epiphenomena) of the physical world.[29] This view has been defended most strongly in recent times by Frank Jackson.[33]

4) Property dualism asserts that when matter is organized in the appropriate way (i.e. in the way that living human bodies are organized), mental properties emerge. Hence, it is a sub-branch of emergent materialism.[8] These emergent properties have an independent ontological status and cannot be reduced to, or explained in terms of, the physical substrate from which they emerge. This position is espoused by David Chalmers and has undergone something of a renaissance in recent years.[34]

Monist solutions to the mind-body problem

In contrast to dualism, monism states that there are no fundamental divisions. Today, the most common forms of monism in Western philosophy are physicalist.[10] Physicalistic monism asserts that the only existing substance is physical, in some sense of that term to be clarified by our best science.[35] However, a variety of formulations (see below) are possible. Another form of monism, idealism, states that the only existing substance is mental. Although pure idealism, such as that of George Berkeley, is uncommon in contemporary Western philosophy, a more sophisticated variant called panpsychism, according to which mental experience and properties may be at the foundation of physical experience and properties, has been espoused by some philosophers such as William Seager.[36]

Phenomenalism is the theory that representations (or sense data) of external objects are all that exist. Such a view was briefly adopted by Bertrand Russell and many of the logical positivists during the early 20th century.[37] A third possibility is to accept the existence of a basic substance which is neither physical nor mental. The mental and physical would then both be properties of this neutral substance. Such a position was adopted by Baruch Spinoza[9] and was popularized by Ernst Mach[38] in the 19th century. This neutral monism, as it is called, resembles property dualism.

Physicalistic monisms

Behaviorism

Behaviorism dominated philosophy of mind for much of the 20th century, especially the first half.[10] In psychology, behaviorism developed as a reaction to the inadequacies of introspectionism.[35] Introspective reports on one's own interior mental life are not subject to careful examination for accuracy and can not be used to form predictive generalizations. Without generalizability and the possibility of third-person examination, the behaviorists argued, psychology cannot be scientific.[35] The way out, therefore, was to eliminate the idea of an interior mental life (and hence an ontologically independent mind) altogether and focus instead on the description of observable behavior.[39]

Parallel to these developments in psychology, a philosophical behaviorism (sometimes called logical behaviorism) was developed.[35] This is characterized by a strong verificationism, which generally considers unverifiable statements about interior mental life senseless. For the behaviorist, mental states are not interior states on which one can make introspective reports. They are just descriptions of behavior or dispositions to behave in certain ways, made by third parties to explain and predict others' behavior.[40]

Philosophical behaviorism, notably held by Wittgenstein, has fallen out of favor since the latter half of the 20th century, coinciding with the rise of cognitivism.[1] Cognitivists reject behaviorism due to several perceived problems. For example, behaviorism could be said to be counter-intuitive when it maintains that someone is talking about behavior in the event that a person is experiencing a painful headache.

Identity theory

Type physicalism (or type-identity theory) was developed by John Smart[17] and Ullin Place[41] as a direct reaction to the failure of behaviorism. These philosophers reasoned that, if mental states are something material, but not behavior, then mental states are probably identical to internal states of the brain. In very simplified terms: a mental state M is nothing other than brain state B. The mental state "desire for a cup of coffee" would thus be nothing more than the "firing of certain neurons in certain brain regions".[17]

The classic Identity theory and Anomalous Monism in contrast. For the Identity theory, every token instantiation of a single mental type corresponds (as indicated by the arrows) to a physical token of a single physical type. For anomalous monism, the token-token correspondences can fall outside of the type-type correspondences. The result is token identity.

Despite its initial plausibility, the identity theory faces a strong challenge in the form of the thesis of multiple realizability, first formulated by Hilary Putnam.[19] It is obvious that not only humans, but many different species of animal can, for example, experience pain. However, it seems highly unlikely that all of these diverse organisms with the same pain experience are in the same identical brain state. And if the latter is the case, then pain cannot be identical to a specific brain state. The identity theory is thus empirically unfounded.[19]

On the other hand, even granted all above, it does not follow that identity theories of all types must be abandoned. According to token identity theories, the fact that a certain brain state is connected with only one "mental" state of a person does not have to mean that there is an absolute correlation between types of mental states and types of brain state. The type-token distinction can be illustrated by a simple example: the word "green" contains four types of letters (g, r, e, n) with two tokens (occurrences) of the letter e along with one each of the others.
The idea of token identity is that only particular occurrences of mental events are identical with particular occurrences or tokenings of physical events.[42] Anomalous monism (see below) and most other non-reductive physicalisms are token-identity theories.[43] Despite these problems, there is a renewed interest in the type identity theory today, primarily due to the influence of Jaegwon Kim.[17]

What all these different varieties of functionalism share in common is the thesis that mental states are characterized by their causal relations with other mental states and with sensory inputs and behavioral outputs. That is, functionalism abstracts away from the details of the physical implementation of a mental state by characterizing it in terms of non-mental functional properties. For example, a kidney is characterized scientifically by its functional role in filtering blood and maintaining certain chemical balances. From this point of view, it does not really matter whether the kidney be made up of organic tissue, plastic nanotubes or silicon chips: it is the role that it plays and its relations to other organs that define it as a kidney.[44]

Nonreductive physicalism

Many philosophers hold firmly to two essential convictions with regard to mind-body relations: 1) Physicalism is true and mental states must be physical states, but 2) All reductionist proposals are unsatisfactory: mental states cannot be reduced to behavior, brain states or functional states.[35] Hence, the question arises whether there can still be a non-reductive physicalism. Donald Davidson's anomalous monism[18] is an attempt to formulate such a physicalism.

A basic idea which all non-reductive physicalists share in common is the thesis of supervenience: mental states supervene on physical states, but are not reducible to them. "Supervenience" therefore describes a functional dependence: there can be no change in the mental without some change in the physical.[46]

Emergentism

Emergentism is a form of "nonreductive physicalism" that involves a layered view of nature, with the layers arranged in terms of increasing complexity and each corresponding to its own special science. Some philosophers hold that emergent properties causally interact with more fundamental levels, while others maintain that higher-order properties simply supervene over lower levels without direct causal interaction. The latter group therefore holds a stricter definition of emergentism, which can be rigorously stated as follows: a property P of composite object O is emergent if it is metaphysically possible for another object to lack property P even if that object is composed of parts with intrinsic properties identical to those in O and has those parts in an identical configuration. Although AL Engleman, in his book "Expressions: A Philosophy of Mind" states that it is all mind, and hence all and only mind emerges as causal agents, since what emerges is an expression of the lower levels. Mind emerges from the processes of it's own own Energy systems. Emergence gives rise to Intentionality for only Emergengent Energy can effect,and hence be causal, as in "Effort produces Effects".[47]

Sometimes emergentist use the example of water having a new property when Hydrogen H and Oxygen O combine to form H20 (water). In this example there "emerges" a new property of a transparent liquid that would not have been predicted by understanding hydrogen and oxygen as a gas, but physicists would claim that they could predict outcome of these two elements combining so it may not be the best of examples. But such is to be a similar case with physical properties of the brain giving rise to a mental state. Emergentists try to solve the notorious mind-body gap this way. One problem for emergentism is the idea "causal closure" in the world that does not allow for a mind-to-body causation.[48] Except for the work of AL Engleman in the above who has taken the Blake route in which the body and all its parts make up the Mind. Some support for this in medical transplant cases, where the transplant recipient has memories or recollections from the donor's experiences.[49]

Eliminative materialism

If one is a materialist but believes that not all aspects of our common sense psychology will find reduction to a mature cognitive-neuroscience, and that a non-reductive materialism is mistaken, then one can adopt a final, more radical position: eliminative materialism.

There are several varieties of eliminative materialism, but all maintain that our common-sense "folk psychology" badly misrepresents the nature of some aspect of cognition. Eliminativists regard folk psychology as a falsifiable theory, and one likely to be falsified by future cognitive-neuroscientific research. Should better theories of the mental come along they argue, we might need to discard certain basic common-sense mental notions that we have always taken for granted, such as belief, consciousness, emotion, qualia, or propositional attitudes.

Eliminativists such as Patricia and Paul Churchland argue that while folk psychology treats cognition as fundamentally sentence-like, the non-linguistic vector/matrix model of neural network theory or connectionism will prove to be a much more accurate account of how the brain works.[15]

The Churchlands often invoke the fate of other, erroneous popular theories and ontologies which have arisen in the course of history.[15][16] For example, Ptolemaic astronomy served to explain and roughly predict the motions of the planets for centuries, but eventually this model of the solar system was eliminated in favor of the Copernican model. The Churchlands believe the same eliminative fate awaits the "sentence-cruncher" model of the mind in which thought and behavior are the result of manipulating sentence-like states called "propositional attitudes."

Linguistic criticism of the mind-body problem

Each attempt to answer the mind-body problem encounters substantial problems. Some philosophers argue that this is because there is an underlying conceptual confusion.[50] These philosophers, such as Ludwig Wittgenstein and his followers in the tradition of linguistic criticism, therefore reject the problem as illusory.[51] They argue that it is an error to ask how mental and biological states fit together. Rather it should simply be accepted that human experience can be described in different ways - for instance, in a mental and in a biological vocabulary. Illusory problems arise if one tries to describe the one in terms of the other's vocabulary or if the mental vocabulary is used in the wrong contexts.[51] This is the case, for instance, if one searches for mental states of the brain. The brain is simply the wrong context for the use of mental vocabulary - the search for mental states of the brain is therefore a category error or a sort of fallacy of reasoning.[51]

Today, such a position is often adopted by interpreters of Wittgenstein such as Peter Hacker.[50] However, Hilary Putnam, the inventor of functionalism, has also adopted the position that the mind-body problem is an illusory problem which should be dissolved according to the manner of Wittgenstein.[52]

Naturalism and its problems

The thesis of physicalism is that the mind is part of the material (or physical) world. Such a position faces the problem that the mind has certain properties that no other material thing seems to possess. Physicalism must therefore explain how it is possible that these properties can nonetheless emerge from a material thing. The project of providing such an explanation is often referred to as the "naturalization of the mental."[35] Some of the crucial problems that this project attempts to resolve include the existence of qualia and the nature of intentionality.[35]

Qualia

Many mental states have the property of being experienced subjectively in different ways by different individuals.[23] For example, it is characteristic of the mental state of pain that it hurts. Moreover, your sensation of pain may not be identical to mine, since we have no way of measuring how much something hurts nor of describing exactly how it feels to hurt. Philosophers and scientists ask where these experiences come from. Nothing indicates that a neural or functional state can be accompanied by such a pain experience. Often the point is formulated as follows: the existence of cerebral events, in and of themselves, cannot explain why they are accompanied by these corresponding qualitative experiences. The puzzle of why many cerebral processes occur with an accompanying experiential aspect in consciousness seems impossible to explain.[22]

Yet it also seems to many that science will eventually have to explain such experiences.[35] This follows from the logic of reductive explanations. If I try to explain a phenomenon reductively (e.g., water), I also have to explain why the phenomenon has all of the properties that it has (e.g., fluidity, transparency).[35] In the case of mental states, this means that there needs to be an explanation of why they have the property of being experienced in a certain way.

The problem of explaining the introspective, first-person aspects of mental states, and consciousness in general, in terms of third-person quantitative neuroscience is called the explanatory gap.[53] There are several different views of the nature of this gap among contemporary philosophers of mind. David Chalmers and the early Frank Jackson interpret the gap as ontological in nature; that is, they maintain that qualia can never be explained by science because physicalism is false. There are two separate categories involved and one cannot be reduced to the other.[54] An alternative view is taken by philosophers such as Thomas Nagel and Colin McGinn. According to them, the gap is epistemological in nature. For Nagel, science is not yet able to explain subjective experience because it has not yet arrived at the level or kind of knowledge that is required. We are not even able to formulate the problem coherently.[23] For McGinn, on other hand, the problem is one of permanent and inherent biological limitations. We are not able to resolve the explanatory gap because the realm of subjective experiences is cognitively closed to us in the same manner that quantum physics is cognitively closed to elephants.[55] Other philosophers liquidate the gap as purely a semantic problem.

Intentionality

Intentionality is the capacity of mental states to be directed towards (about) or be in relation with something in the external world.[21] This property of mental states entails that they have contents and semantic referents and can therefore be assigned truth values. When one tries to reduce these states to natural processes there arises a problem: natural processes are not true or false, they simply happen.[56] It would not make any sense to say that a natural process is true or false. But mental ideas or judgments are true or false, so how then can mental states (ideas or judgments) be natural processes? The possibility of assigning semantic value to ideas must mean that such ideas are about facts. Thus, for example, the idea that Herodotus was a historian refers to Herodotus and to the fact that he was an historian. If the fact is true, then the idea is true; otherwise, it is false. But where does this relation come from? In the brain, there are only electrochemical processes and these seem not to have anything to do with Herodotus.[20]

Philosophy of mind and science

Humans are corporeal beings and, as such, they are subject to examination and description by the natural sciences. Since mental processes are not independent of bodily processes, the descriptions that the natural sciences furnish of human beings play an important role in the philosophy of mind.[1] There are many scientific disciplines that study processes related to the mental. The list of such sciences includes: biology, computer science, cognitive science, cybernetics, linguistics, medicine, pharmacology, and psychology.[57]

Neurobiology

The theoretical background of biology, as is the case with modern natural sciences in general, is fundamentally materialistic. The objects of study are, in the first place, physical processes, which are considered to be the foundations of mental activity and behavior.[58] The increasing success of biology in the explanation of mental phenomena can be seen by the absence of any empirical refutation of its fundamental presupposition: "there can be no change in the mental states of a person without a change in brain states."[57]

Since the 1980s, sophisticated neuroimaging procedures, such as fMRI (above), have furnished increasing knowledge about the workings of the human brain, shedding light on ancient philosophical problems.

Computer science

Computer science concerns itself with the automatic processing of information (or at least with physical systems of symbols to which information is assigned) by means of such things as computers.[60] From the beginning, computer programmers have been able to develop programs which permit computers to carry out tasks for which organic beings need a mind. A simple example is multiplication. But it is clear that computers do not use a mind to multiply. Could they, someday, come to have what we call a mind? This question has been propelled into the forefront of much philosophical debate because of investigations in the field of artificial intelligence.

Within AI, it is common to distinguish between a modest research program and a more ambitious one: this distinction was coined by John Searle in terms of a weak AI and strong AI. The exclusive objective of "weak AI", according to Searle, is the successful simulation of mental states, with no attempt to make computers become conscious or aware, etc. The objective of strong AI, on the contrary, is a computer with consciousness similar to that of human beings.[61] The program of strong AI goes back to one of the pioneers of computation Alan Turing. As an answer to the question "Can computers think?", he formulated the famous Turing test.[62] Turing believed that a computer could be said to "think" when, if placed in a room by itself next to another room which contained a human being and with the same questions being asked of both the computer and the human being by a third party human being, the computer's responses turned out to be indistinguishable from those of the human. Essentially, Turing's view of machine intelligence followed the behaviourist model of the mind - intelligence is as intelligence does. The Turing test has received many criticisms, among which the most famous is probably the Chinese roomthought experiment formulated by Searle.[61]

The question about the possible sensitivity (qualia) of computers or robots still remains open. Some computer scientists believe that the specialty of AI can still make new contributions to the resolution of the "mind body problem". They suggest that based on the reciprocal influences between software and hardware that takes place in all computers, it is possible that someday theories can be discovered that help us to understand the reciprocal influences between the human mind and the brain (wetware).[63]

Psychology

Psychology is the science that investigates mental states directly. It uses generally empirical methods to investigate concrete mental states like joy, fear or obsessions. Psychology investigates the laws that bind these mental states to each other or with inputs and outputs to the human organism.[64]

An example of this is the psychology of perception. Scientists working in this field have discovered general principles of the perception of forms. A law of the psychology of forms says that objects that move in the same direction are perceived as related to each other.[57] This law describes a relation between visual input and mental perceptual states. However, it does not suggest anything about the nature of perceptual states. The laws discovered by psychology are compatible with all the answers to the mind-body problem already described.

Philosophy of mind in the continental tradition

Most of the discussion in this article has focused on the predominant school (or style) of philosophy in modern Western culture, usually called analytic philosophy (sometimes described as Anglo-American philosophy).[65] Other schools of thought exist, however, which are sometimes subsumed under the broad label of continental philosophy.[65] In any case, the various schools that fall under this label (phenomenology, existentialism, etc.) tend to differ from the analytic school in that they focus less on language and logical analysis and more on directly understanding human existence and experience. With reference specifically to the discussion of the mind, this tends to translate into attempts to grasp the concepts of thought and perceptual experience in some direct sense that does not involve the analysis of linguistic forms.[65]

In Georg Wilhelm Friedrich Hegel's Phenomenology of Mind, Hegel discusses three distinct types of mind: the subjective mind, the mind of an individual; the objective mind, the mind of society and of the State; and the Absolute mind, a unity of all concepts. See also Hegel's Philosophy of Mind from his Encyclopedia.[66]

In modern times, the two main schools that have developed in response or opposition to this Hegelian tradition are Phenomenology and Existentialism. Phenomenology, founded by Edmund Husserl, focuses on the contents of the human mind (see noema) and how phenomenological processes shape our experiences.[67]Existentialism, a school of thought founded upon the work of Søren Kierkegaard and Friedrich Nietzsche, focuses on the content of experiences and how the mind deals with such experiences.

An important, though not very well known, example of a philosopher of mind and cognitive scientist who tries to synthesize ideas from both traditions is Ron McClamrock. Borrowing from Herbert Simon and also influenced by the ideas of existential phenomenologists such as Maurice Merleau-Ponty and Martin Heidegger, McClamrock suggests that man's condition of being-in-the-world ("Dasein", "In-der-welt-sein") makes it impossible for him to understand himself by abstracting away from it and examining it as if it were a detached experimental object of which he himself is not an integral part.[68]

Consequences of philosophy of mind

There are countless subjects that are affected by the ideas developed in the philosophy of mind. Clear examples of this are the nature of death and its definitive character, the nature of emotion, of perception and of memory. Questions about what a person is and what his or her identity consists of also have much to do with the philosophy of mind. There are two subjects that, in connection with the philosophy of the mind, have aroused special attention: free will and the self.[1]

Free will

In the context of philosophy of mind, the problem of free will takes on renewed intensity. This is certainly the case, at least, for materialistic determinists.[1] According to this position, natural laws completely determine the course of the material world. Mental states, and therefore the will as well, would be material states, which means human behavior and decisions would be completely determined by natural laws. Some take this reasoning a step further: people cannot determine by themselves what they want and what they do. Consequently, they are not free.[69]

This argumentation is rejected, on the one hand, by the compatibilists. Those who adopt this position suggest that the question "Are we free?" can only be answered once we have determined what the term "free" means. The opposite of "free" is not "caused" but "compelled" or "coerced". It is not appropriate to identify freedom with indetermination. A free act is one where the agent could have done otherwise if it had chosen otherwise. In this sense a person can be free even though determinism is true.[69] The most important compatibilist in the history of the philosophy was David Hume.[70] More recently, this position is defended, for example, by Daniel Dennett,[71] and, from a dual-aspect perspective, by Max Velmans.[72]

On the other hand, there are also many incompatibilists who reject the argument because they believe that the will is free in a stronger sense called libertarianism.[69] These philosophers affirm that the course of the world is not completely determined by natural laws: the will at least does not have to be and, therefore, it is potentially free. The most prominent incompatibilist in the history of philosophy was Immanuel Kant.[73] Critics of this position accuse the incompatibilists of using an incoherent concept of freedom. They argue as follows: if our will is not determined by anything, then we desire what we desire by pure chance. And if what we desire is purely accidental, we are not free. So if our will is not determined by anything, we are not free.[69]

The self

The philosophy of mind also has important consequences for the concept of self. If by "self" or "I" one refers to an essential, immutable nucleus of the person, most modern philosophers of mind will affirm that no such thing exists.[74] The idea of a self as an immutable essential nucleus derives from the idea of an immaterial soul. Such an idea is unacceptable to most contemporary philosophers, due to their physicalistic orientations, and due to a general acceptance among philosophers of the scepticism of the concept of 'self' by David Hume, who could never catch himself doing, thinking or feeling anything.[75] However, in the light of empirical results from developmental psychology, developmental biology and neuroscience, the idea of an essential inconstant, material nucleus - an integrated representational system distributed over changing patterns of synaptic connections - seems reasonable.[76] The view of the self as an illusion is widely accepted by many philosophers, such as Daniel Dennett and Thomas Metzinger.